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  1. #1

    2 Hot Air Splits or 1 + A/C only in the attic ?

    I would like to ask the Pros on their opinion on a new 2900 sq ft 4 BR. home I did the electrical for but now with two weeks before sheet rock, the A/C contractor is too swamped to get it done in time so the GC & I were looking to install the system(s) and have him sweat and charge it. I am a licensed electrician & oil burner tech that does lots of HVAC controls residential & commercial in Boston.

    The last home we built was a 3 zoned, 3 ton 2300 sq ft home that had a 2 stage vari speed American Standard split with natural gas hot air in the attic.
    Every home the GC builds has 6" exterior walls and nice low e windows and the folks that bought the home are very pleased with the unit and are amazed at their low energy bills using it.

    The new home is bigger but built the same but there is no natural gas on the street and the GC does not care for oil heat so a 500 gallon propane tank is going in to feed everything with a flame and my supply house only sells Goodman and the GC want a consumer recognized name brand to boast.

    "The Question", what would be the most practical and best bang for the buck? 1). Having two 2 Ton / 70KBTU Propane splits, 1 in the cellar feeding the first floor and 1 in the attic feeding the second floor and I'm thinking zone motors to defer the returns from sucking from the ceilings during A/C mode and from the floors during heating mode...or
    2). having one 2 Ton A-coil on a 150K propane hot air furnace that would heat the whole house but only cool the first floor and another 2 Ton evap fan box in the attic with high velocity flex to cool the second floor, my idea, but also 3). have 2 - 2 Ton compressors or is there a popular name brand unit that would have 2 - 2 Ton Scroll compressors built in to save space outside, time & money?
    4). Having done many systems for a big Boston company, I like Carrier best, American Standard 2nd then Trane 3rd and falling fast but would like the opinions of the Pro's on the cost effective way of bidding this job with high end stuff and ideas on zoning the supplies & returns, the big family room has a vaulted ceiling with an exposed open hall way to the master sweet over the 2 car attached garage.
    Thanks for your time, AL

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,398
    No furnace of that size has blower compatible with 2 ton without some creative rigging. Might be able to do that with a variable speed unit somehow. Also 2 ton coil above a huge furnace would be a considerable pressure drop and restriction.

    First step is a good accurate load calc to see what you need. Then decide how you are going to do it.

    Obviously propane is an expensive fuel. Is electricity outrageous in your area too? Otherwise 2 electric furnaces and 2 heat pumps sized properly may work. If you do propane, maybe dual fuel? I'd think 2 furnaces and 2 heat pumps for this route as well.

  3. #3
    Join Date
    Jul 2012
    Location
    Stratford
    Posts
    27
    Hydro air?

  4. #4
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,512
    150000 btu in a 2900 square ft well insulated sounds excessive to mee

  5. #5
    Join Date
    Jul 2005
    Location
    Boston/Cape Cod
    Posts
    66
    Well do you have a sheet metal license, which is now required in MA for this type work? And the only correct way to answer your questions is to do a proper heat loss/gain. This from a licensed oil tech with a masters MA SM license

    P.S. Special license is also needed for propane
    southshorejohn

  6. #6
    Thanks for the input men, hydro air was already shot down by the GC as being over complicated although I liked the idea having the option to put in kick toe heaters and radiant in the baths etc. and Yes 150K (in) is over kill. I was going to see who made what size in the 130K - 150K and thinking back to the last home who's buyers finished off the attic in the bottom of the ninth inning. luckily I left an extra 12/2 romex up there and the end of the lighting run etc. and this new attic you could have a pool table in it's that big.
    The propane company is setting the tank and the licensed plumber is doing the tie in's.
    Never knew you needed a sheet metal license to run flex and boots every where, thanks.
    Well South Shore John, I'm sure you are booked solid this time of year but if not? This house is on the SS and the GC would listen to any real licensed / insured HVAC pro on getting these in before the sheet rock goes up in 2 weeks, let me know.
    Thanks for the reply's men,
    AL

  7. #7
    Join Date
    Jul 2005
    Location
    Boston/Cape Cod
    Posts
    66
    Quote Originally Posted by Kenney5454 View Post
    Thanks for the input men, hydro air was already shot down by the GC as being over complicated although I liked the idea having the option to put in kick toe heaters and radiant in the baths etc. and Yes 150K (in) is over kill. I was going to see who made what size in the 130K - 150K and thinking back to the last home who's buyers finished off the attic in the bottom of the ninth inning. luckily I left an extra 12/2 romex up there and the end of the lighting run etc. and this new attic you could have a pool table in it's that big.
    The propane company is setting the tank and the licensed plumber is doing the tie in's.
    Never knew you needed a sheet metal license to run flex and boots every where, thanks.
    Well South Shore John, I'm sure you are booked solid this time of year but if not? This house is on the SS and the GC would listen to any real licensed / insured HVAC pro on getting these in before the sheet rock goes up in 2 weeks, let me know.
    Thanks for the reply's men,
    AL
    That's for the offer, but I learned to stay away from GC's over 20 years ago P.S. This job sounds like a oil fired direct vent boiler along with hydro-air would have been the way to go, propane just costs to much in this area, but seeing it more, as the margin is better than oil now a days.
    southshorejohn

  8. #8
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    3,958
    I've found on well insulated homes there isn't much need for heat upstairs if the downstairs is kept warm. For as little as it runs upstairs a standard A/C with 5KW of electric heat strips is plenty for most homes in our area. The extra cost of installing a furnace doesn't have a reasonable payback time, even when hooked to much cheaper natural gas.

    In our area electric resistance heat is actually cheaper to run than propane, YMMV.

  9. #9
    Well propane is the way this home is going, the 500 gallon tank was dropped in the hole today. I told him of the replies I got here and he just reiterated that oil prices scare people and that propane is only $2.50 a gallon not considering how many BTUs per gallon etc. but the hydro therm or hydronic coils in the fan boxes with a combi-boiler peaked the GCs and plumbers interest. Now all I have to do now is piece together a package that has a combination hot water priority boiler that is in the 90's % efficiency that can keep up with New England winters and 98 degree days in the summer. 1 HVAC contractors bid called for a 2.5 Ton for the second floor with the master suite having a zone off it and a 2 Ton split for the first. The other was a 3 split system, two 2 Tons & a 1.5 over the master which he thought was over kill.
    I agree with you S.S.John about GC's nickle & dimeing you, I just want to keep busy with a guy who has 3 houses going than just sitting on my butt until my number is called, maybe 6 to 9 months for now and since no one can get this system installed for him in the next two weeks I thought I would throw a bid in "IF" possible, T&M

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